188宝金博页面版

  • 图案背景
  • 纯色背景
视图
标记
批注
批注本地保存成功，开通会员云端永久保存 去开通
一泓清水

上传于：2012-01-21

粉丝量：146

该文档贡献者很忙，什么也没留下。


  • 相关
  • 目录
  • 笔记
  • 书签

188宝金博页面版:更多相关文档

  • 雅思阅读实战训练(2)

    星级： 17 页

  • 雅思阅读实战训练(2)

    星级： 17 页

  • 雅思阅读实战训练(2)

    星级： 17 页

  • 雅思阅读实战训练(2)

    星级： 17 页

  • 雅思阅读实战训练(2)

    星级： 17 页

  • 雅思阅读实战训练(2)10772

    星级： 17 页

  • 雅思阅读实战训练

    星级： 74 页

  • 雅思阅读实战训练(4)

    星级： 18 页

  • 雅思阅读实战训练（3）

    星级： 24 页

  • 雅思阅读实战训练(1)

    星级： 15 页

  • 雅思阅读实战训练(4)

    星级： 18 页

  • 雅思阅读实战训练(1)

    星级： 15 页

  • 雅思阅读实战训练(3)

    星级： 24 页

  • 雅思阅读实战训练（一）

    星级： 6 页

  • 雅思阅读实战训练（3）

    星级： 24 页

暂无目录

点击鼠标右键菜单,创建目录

    暂无笔记

    选择文本，点击鼠标右键菜单，添加笔记

    暂无书签

    在左侧文档中，点击鼠标右键，添加书签

    188宝金博页面版: 雅思阅读实战训练（2）

    下载积分： 200

    内容提示： 雅思阅读实战训练(五) ★Don't wash those fossils! Standard museum practice can wash away DNA. 1 . Washing, brushing and varnishing fossils — all standard conservation treatments used by many fossil hunters and museum curators alike — vastly reduces the chances of recovering ancient DNA. 2. Instead, excavators should be handling at least some of their bounty with gloves, and freezing samples as they are found, dirt and all, concludes a paper in the Proceedings of the National Academy of Sciences t...

    文档格式：PDF | 页数：17 | 浏览次数：46 | 上传日期：2012-01-21 13:49:51 | 文档星级：
    雅思阅读实战训练(五) ★Don't wash those fossils! Standard museum practice can wash away DNA. 1 . Washing, brushing and varnishing fossils — all standard conservation treatments used by many fossil hunters and museum curators alike — vastly reduces the chances of recovering ancient DNA. 2. Instead, excavators should be handling at least some of their bounty with gloves, and freezing samples as they are found, dirt and all, concludes a paper in the Proceedings of the National Academy of Sciences today. 3. Although many palaeontologists know anecdotally that this is the best way to up the odds of extracting good DNA, Eva-Maria Geigl of the Jacques Monod Institute in Paris, France, and her colleagues have now shown just how important conservation practices can be. This information, they say, needs to be hammered home among the people who are actually out in the field digging up bones. 4. Geigl and her colleagues looked at 3,200-year-old fossil bones belonging to a single individual of an extinct cattle species, called an aurochs. The fossils were dug up at a site in France at two different times — either in 1 947, and stored in a museum collection, or in 2004, and conserved in sterile conditions at -20 ºC. 5. The team's attempts to extract DNA from the 1 947 bones all failed. The newly excavated fossils, however, all yielded DNA. 6. Because the bones had been buried for the same amount of time, and in the same conditions, the conservation method had to be to blame says Geigl. "As much DNA was degraded in these 57 years as in the 3,200 years before," she says. Wash in, wash out 7. Because many palaeontologists base their work on the shape of fossils alone, their methods of conservation are not designed to preserve DNA, Geigl explains. 8. The biggest problem is how they are cleaned. Fossils are often washed together on-site in a large bath, which can allow water — and contaminants in the form of contemporary DNA — to permeate into the porous bones. "Not only is the authentic DNA getting washed out, but contamination is getting washed in," says Geigl. 9. Most ancient DNA specialists know this already, says Hendrik Poinar, an evolutionary geneticist at McMaster University in Ontario, Canada. But that doesn't mean that best practice has become widespread among those who actually find the fossils. 1 0. Getting hold of fossils that have been preserved with their DNA in mind relies on close relationships between lab-based geneticists and the excavators, says

    阅读了该文档的用户还阅读了这些文档

    188宝金博页面版:关于我们

    188宝金博页面版:帮助中心

    188宝金博页面版:关注我们

    • 新浪微博

    关注188宝金博页面版公众号

    188宝金博页面版
    阅读
    APP
    阅读
    返回
    顶部
    188宝金博页面版官网登录在线平台入口（2026已更新）—江苏协昌电子科技股份有限公司